Inductively coupled charger

ABSTRACT

A device includes a charge controller to regulate a battery output voltage based on an input voltage and an input current received from a charging circuit. A loop controller monitors the input voltage and the input current to generate a feedback signal to adjust the input voltage to the charge controller.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. Nonprovisional patentapplication Ser. No. 13/334,700 filed Dec. 22, 2011 (now U.S. Pat. No.9,331,520), the entirety of which is incorporated by reference herein.

BACKGROUND

Inductive chargers utilize an electromagnetic field to transfer energy.A charging station sends energy through inductive coupling to anelectrical device, which stores the energy in batteries, for example.Inductive chargers typically use a first induction coil to provide analternating electromagnetic field from within a charging base station,and a second induction coil in a portable device that receives powerfrom the electromagnetic field and converts it back into electricalcurrent to charge the battery. The two induction coils in proximitycombine to form an electrical transformer.

SUMMARY

An inductively coupled charger is provided. In one example, a device isprovided that includes a charge controller to regulate a battery outputvoltage based on an input voltage and an input current received from acharging circuit. A loop controller can be provided that monitors theinput voltage and the input current to generate a feedback signal toadjust the input voltage to the charge controller.

In another example, a device includes a charge controller to regulate abattery based on an input voltage and an input current received from acharging circuit. A first loop controller monitors the input voltage togenerate a first feedback signal to adjust the input voltage to thecharge controller. A second loop controller monitors the input currentto generate a second feedback signal to adjust the input voltage to thecharge controller.

In yet another example, a method is provided. The method includescontrolling a battery voltage and current via an inner control loopbased on an input voltage and an input current received from a chargingcircuit. This includes employing a transmitter controller to control theinput voltage and the input current in the charging circuit. The methodincludes employing a first outer control loop to monitor the inputvoltage and to generate a first feedback signal to adjust the inputvoltage to the charge controller. The method also includes employing asecond outer control loop to monitor the input current and to generate asecond feedback signal to adjust the input voltage to the inner controlloop.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of an inductively coupled charger device.

FIG. 2 illustrates an example of an inductively coupled charger devicethat employs a single outer loop controller to control battery loadvoltage and current.

FIG. 3 illustrates an example of an inductively coupled charger devicethat employs two outer loop controllers to control battery load voltageand current.

FIG. 4 illustrates an example transmitter and receiver circuit that canbe utilized as part of an inductively coupled charger device.

FIG. 5 illustrates an example method for charging a battery viainductively coupled charging.

DETAILED DESCRIPTION

FIG. 1 illustrates an example of an inductively coupled charger device100. The inductively coupled charger device 100 (also referred to ascharger device) provides multiple levels of closed-loop voltage,current, and/or temperature control to efficiently control operations ofthe charger (e.g., wireless cell phone battery charger). The chargerdevice 100 can include an inductively coupled charging circuit 110 (alsoreferred to as charging circuit) that supplies regulated DC power shownas VREG. The charging circuit 110 can include a transformer (not shown)to wirelessly transmit power and can include a transmitter controller(not shown) to control voltage supplied to the transformer. An exampleof the charging circuit will be described below with respect to FIG. 4.The regulated voltage VREG can be sensed via current sense circuit 130which supplies current I-SENSE to a charge controller 140 and loopcontroller 150 that act in conjunction to control a load voltage andcurrent VI-LOAD supplied to a battery 170. The charge controller 140receives a reference voltage VO-REF from the loop controller 150 whilemonitoring I SENSE and VI-LOAD. The charge controller 140 controls theload voltage and current VI-LOAD via a regulation switch 190 thatsupplies both voltage and current to charge the battery 170.

As an example, the charge controller 140 acts as an inner-loopcontroller for the output voltage and current VI-LOAD whereas the loopcontroller 150 acts as an outer-loop controller that controls inputvoltages generated at the charging circuit 110 via feedback 194. Thus,the charge controller 140 and loop controller 150 cooperate with thetransmitter controller in the charging circuit 110 to control the outputvoltage and current VI-LOAD in a closed-loop manner. As shown, the loopcontroller 150 monitors current from I SENSE and voltage VREG togenerate the feedback 194 to the charging circuit 110.

As will be described below with respect to FIG. 3, a second loopcontroller (not shown) can be added to the charger device 100 to provideadditional controls for more efficient generation and control of VI-LOADat the battery 170. For example, one controller can be dedicated tomonitor VREG and generate feedback 194 whereas the second controller canmonitor I SENSE and generate a second feedback (not shown) to thecharging circuit as will be illustrated and described with respect toFIG. 3.

The charge controller 140 can include discrete devices configured torespond to both current and voltage feedback from I SENSE and the loopcontroller 150 to control VI-LOAD via the regulation switch 190. Theloop controller 150 can include a processor to execute a controlalgorithm and can include other elements such as an analog-to-digitalconverter (ADC) (e.g., can be an integrated processor and ADC amongother circuit components in the loop controller). The control algorithmcan be employed as a global control loop that couples the transmitterand receiver (shown below with respect to FIG. 4), where the transmitterrefers to the primary side of the inductively coupled charging circuit110 and the receiver refers to the secondary side of the chargingcircuit. In one example, the receiver can monitor and controlsubstantially any variable (e.g., rectifier voltage, output current, andso forth). The receiver can calculate the % difference between themeasured control variable, and the target value for the controlvariable, and sends this value to the transmitter (e.g., %Error=100×(Desired−Actual)/Desired). Upon receiving the % error messagevia feedback 194, the transmitter can execute a local PID(proportional-integral-derivative) loop which can move a controlvariable and attempt to shift the measured peak primary current by the %error value calculated by the receiver. This can change the powerdelivered to the receiver, and thus can drive the receiver controlvariable closer to its target value.

For purposes of simplification of explanation, in the present example,different components of the device 100 are illustrated and described asperforming different functions. However, one of ordinary skill in theart will understand and appreciate that the functions of each of thedescribed components can be performed by one or more differentcomponents, or the functionality of several components can be combinedand executed on a single component.

FIG. 2 illustrates an example of an inductively coupled charger device200 that employs a single outer loop controller 204 to control batteryload voltage and current. The charger device 200 includes an inductivelycoupled charging circuit 210 that generates a regulated DC outputvoltage VREG. A current sense circuit 220 supplies voltage and currentto a regulation switch 224 that in turn controls voltage and currentdelivered to a battery 230. A charge controller 234 controls theregulation switch 224. The charge controller 234 includes an amplifier240 to monitor sensor signal I-SENSE from current sense 220 and anamplifier 244 that monitors battery output voltage. The chargecontroller 234 includes a current source 250 (e.g., charge pump) thatbiases the regulation switch 224. Output from amplifiers 240 and 244 arelogically OR'd via diodes 260 and 264, respectively to control theregulation switch 224 at the output of the current source 250. Aresistor 270 can be employed to establish a reference voltage that isproportional to I-SENSE generated by current sense 220. The referencevoltage can be utilized as a reference to amplifier 240 and as an inputreference to outer loop controller and ADC 274.

The amplifier 240 can monitor various switched inputs at 280 and caninclude a charging reference signal input I-1, a pre-charging referencesignal input I-2, or a thermal-charging reference signal input I-3, forexample, to facilitate control of the regulation switch 224. The inputsat 280 sense current, such as can be converted to voltages forcomparison with I-SENSE reference voltage 270 at amplifier 240. The loopcontroller can include an analog to digital converter (ADC) and canmonitor I SENSE and VREG in addition to an external reference voltageVREF to bias the internal workings of the loop controller and ADC. Afeedback signal 290 can be generated by the loop controller 204, whereinsuch feedback can be provided as a digital signal that can becommunicated via inductive primary and secondary elements of theinductively coupled charging circuit 210. As shown, a voltage inputsignal 294 connected to the battery output voltage can be processed bythe loop controller 204. The loop controller 204 measures input voltageVREG and the battery output voltage and drives the input voltage abovethe output voltage by a suitable amount to operate the regulation switch224 in saturation.

In an example, the charge controller 234 can be a linear chargecontroller utilizing input current sense 220. As shown, two analog loopscan be OR'd together at the output of current source 250, where oneanalog loop can regulate current via amplifier 240 and one analog loopcan regulate voltage via amplifier 244. The device 200 can provide awireless control loop to connect a receiver to a transmitter (insideinductively coupled charging circuit 210), wherein the receiver sendscommands to the transmitter via feedback 290 to control the receiverinput voltage.

As an example, the wireless control loop can operate as follows: theloop controller 204 and ADC can monitor the input voltage, output(battery) voltage, and output current. The loop controller can sendfeedback 290 to the transmitter in the charging circuit 210 to controlthe rectifier voltage (see FIG. 4 below) to the desired value. If thecharge controller 234 is in current regulation, then the loop controller204 can send digital packets via feedback 290 to control the rectifiervoltage to be above the battery voltage by a given margin that can holdthe regulation switch 224 (e.g., FET) in saturation when VDS (voltagedrain to source) is greater than VDSAT (drain saturation voltage). Inthis case, the internal analog loop of the charge controller 234 setsthe value of the output current to the battery 230. Similarly, in apre-charge or thermal fold-back condition, the internal analog loop ofthe charge controller 234 can set the output current, and the wirelessloop thus should control the input voltage to hold the regulation switch224 in saturation. When voltage regulation is active, then the wirelessloop can set the rectifier voltage VREG to a constant level (e.g., 5 V).

FIG. 3 illustrates an example of an inductively coupled charger device300 that employs two outer loop controllers 304 and 306 to controlbattery load voltage and current. Similar to the charger in FIG. 2, thecharger device 300 includes an inductively coupled charging circuit 310that generates a regulated DC output voltage VREG. A sense circuit 320supplies voltage and current to a regulation switch 324 that in turncontrols voltage and current delivered to a battery 330. A chargecontroller 334 controls the regulation switch 324. The charge controller334 includes an amplifier 340 to monitor current I SENSE and anamplifier 344 that monitors battery output voltage. The chargecontroller 334 includes a current source 350 (e.g., charge pump) thatbiases the regulation switch 324. Output from amplifiers 340 and 344 areOR'd via diodes 360 and 364, respectively to control the regulationswitch 324 at the output of the current source 350. A resistor 370 canbe employed to establish a reference voltage that is proportional tocurrent I SENSE. The reference voltage can be utilized as a reference toamplifier 340 and as an input reference to a first outer loop controller1 304.

The amplifier 340 can monitor various switched current inputs at 380 andcan include a charging reference signal input I-1, a pre-chargingreference signal input I-2, or a thermal-charging reference signal inputI-3, for example, to facilitate control of the regulation switch 324during different modes of operation. The inputs at 380 sense current,such as can be converted to voltages for comparison with I-SENSEreference voltage 370 at amplifier 340. The first outer loop controller1 304 can monitor VREG in addition to an external reference voltage VREF384 to bias the internal workings of the ADC. A first feedback signal390 can be generated by the loop controller, wherein such feedback canbe provided as a digital signal that is communicated via inductiveprimary and secondary elements of the inductively coupled chargingcircuit 310. A voltage output signal 392 can be generated by the loopcontroller 1 304 and employed as a reference signal (e.g., signal tocommunicate the desired battery voltage level) by the amplifier 344.

As shown, the device 300 can include a second outer loop controller 2 at306 to monitor current I SENSE and monitor switched input currents 380via voltage point 396 and input 397. A second feedback 398 is providedto the charging circuit 310 representing control feedback for current.It is noted that the first feedback 390 and the second feedback 398could alternatively be multiplexed into the same communications channelcommunicating back to the inductively coupled charging circuit 310.

As shown, the loop controller of FIGS. 1 and 2 can be segmented into anI-channel controller represented as the second controller 306 andV-channel controller represented as the first controller 304. Onedifference in the charger 300 and the charger 200 depicted in theexample of FIG. 2 is in how the feedback messages at 390 and 398 arecomputed and sent. In the charger of FIG. 2, the feedback can be sent tocontrol the rectifier voltage to a certain level, and to ensure theregulation switch stays in saturation. In the charger 300, the rectifiervoltage VREG can still be controlled while the voltage loop is activevia amplifier 344. Additionally, the output current can be controlleddirectly when the current loop is active via amplifier 340.

As a further example, in the charger 300, the output current to thebattery 330 can be controlled as follows: In general, the loopcontroller 2 at 306 can have a certain reference voltage at 399 (e.g.,1.1V which is below analog loop regulation voltage). When the loopcontroller 2 at 306 detects that the current has reached a definedregulation threshold, then it can send messages to the transmitter tocontrol the current to this level via feedback 398, irrespective of theactual rectifier voltage.

In practice, the loop controlled by loop controller 306 may beattempting to reduce the output current, thus to perform this function,the loop may have to reduce the rectifier voltage. Since the loopcontroller 306 current threshold is generally below the analog currentregulation threshold, the regulation switch 324 should operate intriode-mode to reach this operating point. This helps to ensure that fora given regulation switch RDS-ON parameter, for example, the receivershould be maximally efficient at any current regulation point.

In some conventional battery chargers, thermal regulation can beimplemented by reducing the charge current regulation threshold inproportion to increasing die temperature of the regulation switch, whenthe die temperature exceeds a certain threshold (e.g., 125° C.), whichmay be an inefficient and unstable means of operation. In practice, thistype of control can drive the output current to a low value whileconcurrently driving VREG to a high value, which can cause temperatureto drop out of the thermal regulation region. This may cause the chargecurrent to return to its original value, which may cause the receiver toenter the thermal regulation region in a subsequent cycle. In thismanner, the receiver may oscillate in and out of thermal regulation. Inthe device 300, such stability and efficiency problems are mitigatedwith a thermal regulation loop provided by the second loop controller306, and thus can suitably operate at the thermal limit (e.g., maximumcurrent) for a given system as described below.

Regarding thermal regulation, when the receiver temperature operatesabove the thermal limit, the current regulation threshold can drop toreduce the charge current via regulation switch 324. Since this voltageis also the reference voltage 397 for the I-channel controller 306,however, the wireless loop can automatically send messages via feedback398 to the transmitter to reduce the charge current to reducetemperature. In general, the only manner for the system to reduce chargecurrent is to reduce input voltage at the transmitter, which impliesreceiver power dissipation is reduced. Since the thermal loop operatesin a manner that power dissipation is monotonically reduced, thisthermal control loop is substantially stable.

FIG. 4 illustrates an example transmitter and receiver circuit 400 thatcan be utilized as part of an inductively coupled charger device, suchas disclosed herein (e.g., FIGS. 1-3). An inductively coupled chargingcircuit as previously described in FIGS. 1-3 is represented by dashedline 402. A transformer 404 couples energy between a transmitter 408 andreceiver 410 that are employed to charge a battery 414. The transmitter408 includes a controller 416 (e.g., PID controller) that drives powertransistors 418 and 420 which in turn drive the primary side of thetransformer 404. An impedance matching capacitor 424 can be provided.Feedback 428 is received from the receiver 410 and can be developedacross resistor 430. The receiver 410 can include a matching capacitor434 which supplies secondary voltage from the transformer 404 to arectifier 440 to generate rectified DC voltage VREG. The voltage VREG issupplied to a charge controller 450 which regulates voltage and currentto the battery 414 via analog controls as previously described. Aregulator smoothing capacitor can be provided at 454. As shown, a loopcontroller 460 (e.g., loop controller 150 of FIG. 1) can be providedwhich supplies feedback via transistors 464 and 470. Capacitors 474 and480 can be employed to couple the feedback to the secondary of thetransformer 404. The feedback via transistors 464 and 470 can correspondto the feedback 290 shown in FIG. 2.

In view of the foregoing structural and functional features describedabove, an example method will be better appreciated with reference toFIG. 5. While, for purposes of simplicity of explanation, the method isshown and described as executing serially, it is to be understood andappreciated that the method is not limited by the illustrated order, asparts of the method could occur in different orders and/or concurrentlyfrom that shown and described herein. Such method can be executed byvarious components configured in an IC or a controller, for example.

FIG. 5 illustrates an example method for charging a battery viainductively coupled charging. Proceeding to 510, the method 500 includescontrolling a battery voltage and current via an inner control loop(e.g., charge controller 140 of FIG. 1) based on an input voltage and aninput current received from a charging circuit at 510. At 520, themethod 500 includes employing a transmitter controller (e.g., controller416 of FIG. 4) to control the input voltage and the input current in thecharging circuit. At 530, the method 500 includes employing a firstouter control loop (e.g., controller 304 of FIG. 3) to monitor the inputvoltage and to generate a first feedback signal to adjust the inputvoltage to the charge controller. At 540, the method 500 includesemploying a second outer control loop (e.g., controller 306 of FIG. 3)to monitor the input current and to generate a second feedback signal toadjust the input voltage to the inner control loop. The transmittercontroller can utilize a PID loop to control the input voltage and theinput current in the charging circuit, for example. The method 500 canalso include utilizing a regulation switch to control the batteryvoltage.

What have been described above are examples. It is, of course, notpossible to describe every conceivable combination of components ormethodologies, but one of ordinary skill in the art will recognize thatmany further combinations and permutations are possible. Accordingly,the disclosure is intended to embrace all such alterations,modifications, and variations that fall within the scope of thisapplication, including the appended claims. As used herein, the term“includes” means includes but not limited to, the term “including” meansincluding but not limited to. The term “based on” means based at leastin part on. Additionally, where the disclosure or claims recite “a,”“an,” “a first,” or “another” element, or the equivalent thereof, itshould be interpreted to include one or more than one such element,neither requiring nor excluding two or more such elements.

What is claimed is:
 1. A method, comprising: controlling a batteryvoltage and current via an inner control loop based on an input voltageand an input current received from an inductively coupled chargingcircuit, the inner control loop including a charge controller thatprovides the battery voltage and current from the input voltage and theinput current, the charge controller controlling the battery voltage andcurrent based on monitoring the input current relative to a selected oneof a plurality of references; controlling, via an inductively coupledtransmitter controller within the inductively coupled charging circuit,the input voltage and the input current in the charging circuit;monitoring the input voltage, via a first outer control loop thatmonitors the input voltage relative to a voltage reference, to generatea first inductively coupled feedback signal that is inductively coupledto the transmitter controller to adjust the input voltage to the chargecontroller; and monitoring the input current, via a second outer controlloop that monitors the input current relative to the selected reference,to generate a second inductively coupled feedback signal inductivelycoupled to the transmitter controller, to adjust the input voltage tothe inner control loop.
 2. The method of claim 1, wherein thetransmitter controller utilizes a PID (proportional-integral-derivative)loop to control the input voltage and the input current in the chargingcircuit.
 3. The method of claim 2, further comprising controlling thebattery voltage and current by utilizing a regulation switch to controlthe battery voltage.
 4. The method of claim 1, wherein monitoring theinput current relative to a selected one of a plurality of referencesfurther comprises selecting a reference from a charging reference, apre-charging reference, and a temperature reference.
 5. The method ofclaim 1, wherein selecting a reference further comprises programming aselection controller.
 6. The method of claim 1, wherein controlling thebattery voltage and current further comprises the charge controllerreceiving the input current and the selected reference at a firstamplifier having a first output, and receiving the battery voltage and areference voltage at a second amplifier having a second output, andcombining the first output and second output at a node in a wired-ORconfiguration.
 7. The method of claim 6, and further comprising couplingthe node to the regulation switch supplying the battery voltage from theinput voltage, and supplying current to the node to bias the regulationswitch.
 8. The method of claim 1, wherein inductively coupling the firstfeedback signal further comprises coupling the first feedback signal toa secondary winding of a transformer in a receiver circuit of theinductively coupled current charging circuit.
 9. The method of claim 8,wherein inductively coupling the second feedback signal furthercomprises coupling the second feedback signal to the secondary windingof the transformer within the receiver circuit.
 10. The method of claim1, wherein the inductively coupled current charging circuit includes thetransmitter that is coupled to a primary winding of the transformer inthe receiver circuit.
 11. An inductively coupled charger system,comprising: a transmitter circuit inductively coupled to a receivercircuit; a charger controller configured to regulate a battery outputvoltage based on an input voltage from the receiver circuit and an inputcurrent received from a charging circuit; a first loop controllerconfigured to monitor the input voltage to generate a first feedbacksignal to adjust the input voltage to the charge controller; and asecond loop controller configured to monitor the input current togenerate a second feedback signal to adjust the input voltage to thecharge controller, the second loop controller generating the secondfeedback signal based on the input current relative to a reference thatis selected from a plurality of references to adjust a control variable;the transmitter circuit and the receiver circuit to inductively coupleenergy to the charge controller and the first and second loopcontrollers; further comprising a regulation switch that receives theinput voltage to regulate voltage and current at the battery based on acontrol signal from the charge controller; wherein the charge controllerfurther comprises a current sense amplifier to monitor input currentrelative to the selected reference and a voltage sense amplifier tomonitor output voltage to control the regulation switch and wherein thecurrent sense amplifier utilizes the input current as a reference andcompares the reference to a charging reference signal, a pre-chargingreference signal, or a thermal charging reference signal to control ofthe regulation switch; and further comprising a selection controllerconfigured to control which of the plurality of references is providedas a reference signal to the current sense amplifier, the selectedreference signal corresponding to a charging reference signal, apre-charging reference signal, or a thermal charging reference signal.12. A method, comprising: controlling an output voltage and current toan output node for charging a battery, the output voltage and currentformed from an input voltage and an input current from an inductivelycoupled current charging circuit; monitoring the input current relativeto a reference that is one selected from a plurality of referencesselected by a selection circuit, and responsive to the monitoring,controlling the output voltage to the output node; in a first outercontrol loop, monitoring the input voltage relative to a voltagereference to generate a first feedback signal that is inductivelycoupled to a transmitter controller in the inductively coupled currentcharging circuit; and in a second outer control loop, monitoring theinput current relative to the selected one of the plurality ofreferences to generate a second feedback signal, the second feedbacksignal inductively coupled to the transmitter controller in theinductively coupled charging circuit; wherein the transmitter controllerin the inductively coupled charging circuit executes a control algorithmto control the input voltage responsive to the first feedback signal andto the second feedback signal.
 13. The method of claim 12, and furthercomprising programming the selection circuit to output a referencecorresponding to a charge reference, a pre-charge reference, and athermal charging reference.
 14. The method of claim 12, wherein thecontrol algorithm is a PID (proportional-integral-derivative) algorithm.15. The method of claim 12, wherein controlling an output voltage andcurrent to an output node for charging a battery further comprises, in acharge controller circuit, monitoring the output voltage relative to areference voltage using a first amplifier, and outputting a first outputin response, and monitoring the input current relative to the selectedreference using a second amplifier, and outputting a second output inresponse, combining the first and second outputs at a wired-OR node, thenode coupled to control a regulation switch that supplies the inputvoltage to the output node.
 16. The method of claim 15, and furthercomprising coupling a current supply source to supply current to biasthe regulation switch.